In the construction of the passenger compartment, known motor vehicles have an A pillar, a B pillar, and a C pillar, with the B pillar being the middle one of these pillars, extending from a rocker panel at the bottom to a roof structure at the top.
In this case, the B pillar is usually provided with a latch for the front doors (driver's door, passenger's door) and—if provided—hinges for the rear doors; the hinges of the rear doors can also be provided on the C pillar, in which case the latch is likewise provided (on the rear side) of the B pillar in the same way as with sliding doors in the rear region.
The original purpose of the B pillar is on the one hand, to hold the hinges of the rear doors and support the latch of the front doors and on the other hand, to support the roof structure.
In the context of constantly improving crash safety of passenger compartments, however, the B pillar also serves an essential function for the stability of the passenger compartment.
For several years now, it has been common practice to design passenger compartments to be increasingly more rigid and to use heat-treated steels, which are shaped and hardened using the applicant's special methods for press hardening or form hardening. Such formed and hardened steel components and B pillars in particular have a very high strength of Rm≈1,500 MPa.
In the past, it has turned out that uniformly hardened steel components are not optimal for the passenger compartment. Especially in the event of a crash, these components can break since as a result of their high hardness, they also have a certain degree of brittleness and are not able to absorb energy by deforming, but instead are much more likely to break.
In order to improve the crash behavior of such B pillars, it is known for the base of the B pillar in particular to either not be hardened or for it to not be entirely hardened, thus producing more ductile, flexible regions of the B pillar.
Such B pillars are known, for example, from EP 1 180 470 A1 and U.S. Pat. No. 6,820,924.
EP 2 209 696 B1 has disclosed a B pillar for a vehicle, which has, an upper fastening region for fastening to a roof component and a lower fastening region for fastening to a rocker panel; the main section of the B pillar has an essentially martensitic structure with a tensile strength of at least 1,300 MPa and a weaker lower region of the B pillar with a tensile strength of no more than 800 the weaker region has a height of greater than 30 mm, but extends for less than ⅓ of the overall height of the B pillar and is positioned so that the lower fastening region is essentially martensitic. Preferably, the weaker region has a height that is less than ¼ of the overall height of the B pillar, with the weaker region having a height of between 50 mm and 200 mm. In this B pillar, the soft region is spaced significantly apart from a fastening region on the rocker panel. The relatively narrow band with the lower strength, which preferably should be less than 200 mm wide, is particularly situated in the lower half, preferably in the lowest third, of the pillar, but at a significant distance from the B pillar fold resting on the rocker panel.
The object of the invention is to design a B pillar in a crash-optimized way for a motor vehicle.